Potential and diversity of bird species in various land covers in PT BSM, South Sumatera

Birds have an important role in the ecosystem, including as environmental indicators, natural pest controls, and tourist attractions. The existence of birds in a habitat type certainly plays an important role both ecologically and economically. Research that shows the ecological and economic potential of bird species in oil palm plantations is still not widely done. Therefore, research is needed to be able to show the potential and variation of bird species diversity in oil palm plantations. This research was conducted at PT Bina Sawit Makmur (PT BSM) on Desember 2019. The method used was a line transect that was carried out on five different land covers simultaneously. The results showed that a total of 28 species were found. High Conservation Value (HCV) land cover has the highest diversity, richness, and species similarity index values. The potential possessed by bird species in various types of land cover includes natural pest control, economic value animals, and environmental indicators.


Introduction
Birds have an important role in the ecosystem, including they can act as environmental indicators, natural pest controllers, and tourist attractions.The existence of birds in a habitat type certainly plays an important role both ecologically and economically.One of the factors that affect the bird species diversity is the diversity of vegetation.The more diverse the types of vegetation available, the more types of birds that can live in that habitat.In this case, it can be said that changes in land cover can disrupt the diversity of bird species.Oil palm plantations are often accused of causing a decrease in biodiversity, including birds because their diversity is vulnerable to a decrease due to land conversion to oil palm plantations [1].However, the addition of undergrowth species in oil palm plantation can provide habitat for insects [2].Thus increase the number of insect species [3], so that they can provide a food source for insectivorous birds.In addition, the presence of HCV areas in oil palm plantations can also provide a relatively heterogeneous composition of vegetation, thus creating a more varied ecological niche.More tree species will create more ecological niches that allow different types of birds to live together.Many studies on bird diversity in oil palm plantations have been carried out [4,5,6].However, research showing the ecological and economic potential of bird species in oil palm plantations is still limited.This research aimed to identify bird diversity and potential in oil palm plantations.

Methods
Observations were conducted in December 2019 on 5 types of land cover in PT BSM, namely young oil palm plantation (SM), medium oil palm plantation (SS), old oil palm plantation (ST), High Conservation Value area (HCV), and shrubs (SB).The general condition of each research location were showed on Figure 1 for SM, Figure 2 for SS, Figure 3 for ST, Figure 4 for HCV, and Figure 5 for SB.

Observation method
Observations were conducted in December 2019 on five types of land cover in PT BSM, namely young oil palm plantation (SM), medium oil palm plantation (SS), old oil palm plantation (ST), High Conservation Value area (HCV), and shrubs (SB).Observations were conducted on the observation path with a length of 1000 meters and a width of 200 m.Data was collected by 3 times of repetition at each type of land cover.Observations were conducted in the morning (06.00-08.00WIB) and in the afternoon (16.00-18.00WIB).The general condition of each research location were showed on Figure 1 for SM, Figure 2 for SS, Figure 3 for ST, Figure 4 for HCV, and Figure 5 for SB.The diversity of bird species was obtained using the formula: Information: H '= Shannon-Wiener diversity index n = Number of individuals of a particular type ln = natural logarithm N = Number of individuals of all types Pi = Proportion of species

Species richness.
The data were analyzed with Margalef richness index to determine the value of species richness index: Information: Information: E = Evenness Index H' = Shannon-wiener diversity index S = Total species

Guild composition.
Guild composition analysis was done by classifying species of birds that utilize the same type of feed [7].

Result and Discussion
Based on observations, a total of 380 individuals of 28 species are shown in Table 1.Species that can be found in all types of land cover include Pycnonotus aurigaster, Streptopelia chinensis, and Collocalia linchi.Area SB is the land cover with the highest number of species, namely 18 species.While the type of land cover with the least number of species is SS, which is 8 species.Notes: young oil palm plantation (SM), medium oil palm plantation (SS), old oil palm plantation (ST), High Conservation Value area (HCV), and shrubs (SB).
Figure 6 shows a comparison of species richness, diversity and evenness index value.The figure shows although the SB area has the highest species and individuals number, the HCV area has the highest diversity, evenness, and species richness index values than other land cover types.The species diversity index is influenced by the number of individuals of each species.Thus even though the SB area has a highest number of species and the total number of individuals among all, the diversity value of the species diversity index will actually be lower than the HCV area.This is supported by the diversity of plant species in the HCV area which is more diverse, thus allowing for various ecological niches for different types of birds [8].Also, HCV areas in PT BSM is a watersheds which is an important component of biodiversity (Figure 4).The watersheds is an important area because it support source of water for wildlife; support the growth of plants used by wild animals; regulate the microclimate, and become a corridor for migratory animals [9].The value of the species evenness index on all types of land cover is high because it is close to the value of 1.This indicates that in all types of land cover, individuals for each type are evenly distributed.The closer the value to 1 means that the distribution of individuals on the type of land cover is more even.The birds divided into different guild by grouping it based on the type of main food source.Figure 7 shows the composition of the bird species guild in PT BSM.The feeding guild in PT BSM consists of insectivores, carnivores, piscivores, frugivores, and granivores.Bird species belonging to the insectivore are the most common and can be found in all observation areas.This is due to the availability of shrubs and weeds in each observation plot.Shrubland cover types have a high level of insect species diversity compared to other land cover types [10].Also, insects are a source of food that are widely found in and are always available throughout the year [11].Thus, the number of insectivore bird species is abundant in the study site.Besides, the availability of shrubs and weeds also provides lots of seeds as a food source for granivorous birds.The piscivore birds that have been found are 3 species because its distribution depends on riparian areas.Bird species from fish-eating groups or piscivore are mostly water birds that use wetland habitats to find food.Total species of birds with fruit as their main food source is low, namely 2 species, because their distribution is limited to the availability of fruit-producing trees.The guild group with the lowest percentage was the carnivore.This is because the distribution of the carnivore group is influenced by the limited number of prey [7].Based on the guild grouping, the ecological role of birds in PT BSM can be divided into 4, namely pest control, predators, seed dispersers, and weed control.Figure 8 shows the potential of bird species  Insectivorous birds have a role as insect control arthropods, especially those belonging to insect pests [12].Most cases of the role of birds in eradicating insect pests were the result studies on annual tropical plants [13].Fruit-eating birds like Treron vernans and Pycnonotus goiavier acts as a seed dispersal by disposing of it with dirt.Frugivorous birds help the process of releasing seeds from the flesh and skin of the fruit and facilitate seed germination [14].In addition, if there are seeds that cannot be digested by birds, the seeds will be thrown away with feces when the birds move habitat.This can help the process of plant regeneration and distribution [15].
Granivorous birds can act as weed controllers.However, in agricultural context, they are sometimes considered pests.In this case, predatory bird species could help on controlling the population of granivorous birds.The presence of predatory birds as top predators in ecosystems can help control other pest populations such as rats which are often found in oil palm plantations such as PT BSM.Birds of prey also have a high sensitivity to the environment so that it can act as an indicator of a healthy environment [16].In addition to their ecological role, several types of birds also have an economic role because they are included in the list of non-timber forest products (NTFPs) that can be utilized both in the form of live catch and animal products.Bird species included in the list of NTFPs based on the Regulation of the Minister of Forestry Number 35 of 2007 are Falco sp. and Collocalia linchii [17].

Conclusions
The results showed that a total of 28 species were found.High Conservation Value (HCV) land cover has the highest diversity, richness, and species similarity index values.The potential possessed by bird species in various types of land cover includes natural pest control, seed spreader, economic value animals, and environmental indicators.

5 Figure 6 .
Figure 6.Comparison of diversity, richness, and eveness value index in each land cover type

Figure 7 .
Figure 7. Bird guild in PT BSM